| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1995: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1994: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Boiling and condensation heat transfer coefficients and critical heat fluxes in two-phase closed thermosyphons were investigated. THe inside diameter of the thermosyphon tube was 16 mm, and its evaporator and condenser lengths were both 500 mm. As working liquids, water, ethanol, methanol, Freon 123, Freon 134a, pentane and hexane were used, and the tested temperature in the thermosyphon was 40-90ﾟC.In the experiment, after removing air from the closed thermosyphon, it was filled with the working liquid to about 40% of the evaporater inside volume. However, in the case of metanol, the filling liquid quantity was varied from 30 to 60% to examine the effect of it. The results obtained were as follows : 1.The experimental data of boling heat transfer coefficients in the evaporator with alcohols are correlated with the Imura et al. equation, those with water and Freons with the Gross equation and those with hydrocarbons with the Kaminaga-Okamoto equation. Such different results are caused
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by the different relations between the heat transfer coefficients and heat fluxes for each liquid. 2.The wall temperature of the evaporator shows higher values at the lower part for low heat flux. Although this part is considered as being immersed in a liquid pool, it is presumed that the wall temperature rises because of weak boiling. Also, according to the experiment with methanol of different filling quantity, it is prospected that 50% is appropriate judging from the evaporator wall temperature distributions. 3.The experimental data of the condensation heat transfer coefficients are correlated considerably well with the theoretical equation taking account of a surface wave on a condensate film. However, the data of water show lower values as a whole. 4.The critical heat fluxes are correlated fairy well with the Imura et al. and Fukano et al. equations and Katto's theoretical estimation. However, the data of Freon 123, pentane and hexane indicate about 50% larger than those of water, ethanol, methanol and Freon 113. Less
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